Expandable spinal fixation system

ABSTRACT

Expandable spinal fixation assemblies, systems, and methods thereof. An expandable spinal fixation system may include expandable barrel assembly including an upper barrel half and a lower barrel half and a fixed barrel assembly. The fixed barrel assembly is insertable between the upper barrel half and the lower barrel half such that the fixed barrel assembly is clamped between the upper barrel half and the lower barrel half. Each of the expandable barrel assembly and the fixed barrel assembly includes fixation plates adapted to secure spinous processes to the fixation system.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a Continuation-in-Part of U.S. patentapplication Ser. No. 15/012,992, filed on Feb. 2, 2016, the contents ofwhich are incorporated herein in their entirety by reference for allpurposes.

BACKGROUND

Field of the Invention

The present invention relates to spinous process fixation systems.

Description of the Related Art

A variety of medical devices and medical device systems may be implantedwithin a body of a patient to provide support to a portion or portionsof the patient's body. For example, some medical devices may beimplanted and coupled to backbones or portions of the spine of apatient, and may be configured to provide support to the spinal bonestructure of the patient.

Typically, weaknesses in the spine are corrected using devices that fuseone or more vertebrae together. It may be desirable to have animplantable device that provides for structural stability two adjacentvertebrae and to achieve supplemental fusion to treat weaknesses in thespine due to degenerative disc disease, spondylolisthesis, trauma (i.e.,fracture or dislocation), tumors and/or other causes.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

According to one embodiment, an expandable spinal fixation system mayinclude an expandable barrel assembly having an upper barrel half and alower barrel half. The upper barrel half includes an upper barrel distalend and an upper barrel proximal end, distal from the distal end. Theupper barrel proximal end includes a slot formed therein and a concaveinner surface extending between the upper barrel distal end and theupper barrel proximal end. The lower barrel half includes a lower barreldistal end and a lower barrel proximal end, distal from the lower barreldistal end. The lower barrel proximal end includes a tab sized to beslidably inserted into the slot and a concave inner surface extendingbetween the lower barrel distal end and the lower barrel proximal end. Asecuring assembly includes a plate adapted to bias the tab against theupper barrel proximal end and a securing member adapted to releasablybias the plate against the tab. A fixed barrel assembly has a generallytubular body sized to fit between the concave inner surface of the upperbarrel half and the concave inner surface of the lower barrel half.

In one embodiment, the expandable spinal fixation system includes anexpandable barrel assembly having an upper barrel half extending alongan upper longitudinal axis and a lower barrel half extending along alower longitudinal axis generally parallel to the upper longitudinalaxis. The lower longitudinal axis is movable relative to the upperlongitudinal axis. A fixed barrel assembly is adapted to be insertedbetween the upper barrel half and a lower barrel half.

In an alternative embodiment, the expandable spinal fixation systemincludes a fixed barrel assembly and an expandable barrel assemblyhaving an upper barrel half and a lower barrel half slidingly coupled tothe upper barrel half, such that the fixed barrel assembly is insertablebetween the upper barrel half and the lower barrel half and that thelower barrel half slidable toward the upper barrel half to secure thefixed barrel assembly between the upper barrel half and the lower barrelhalf.

In yet another alternative embodiment, an expandable fixation systemcomprises a first longitudinal member and a second longitudinal memberextending generally parallel to the first longitudinal member and beingadjustable relative to the first longitudinal member. A first lateralmember has a first end slidingly disposed along the first longitudinalmember and a second end fixedly disposed along the second longitudinalmember. A second lateral member has a first end slidingly disposed alongthe first longitudinal member and a second end fixedly disposed on thesecond longitudinal member, such that the second lateral member extendsgenerally parallel to the first lateral member.

In still another alternative embodiment, an expandable spinal fixationsystem comprises an expandable barrel assembly having an upper barrelhalf having. The upper barrel half includes an upper barrel proximal endand an upper barrel distal end, distal from the proximal end. A lowerbarrel half includes a lower barrel proximal end and a lower barreldistal end, distal from the lower barrel proximal end. A fixed barrelassembly has a body sized to fit between the upper barrel half and thelower barrel half in one of an anterior-to-posterior direction and alateral direction.

In yet another alternative embodiment, an expandable spinal fixationsystem comprises expandable barrel assembly and the fixed barrelassembly described above, as well as an insertion tool adapted toreleasably engage the upper barrel half and a second finger adapted toreleasably engage the lower barrel half such that operation of theinsertion tool vertically adjusts the upper barrel half with respect tothe lower barrel half.

In still another alternative embodiment, a method of inserting theinventive fixation system is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects, features, and advantages will become more fully apparentfrom the following detailed description, the appended claims, and theaccompanying drawings in which like reference numerals identify similaror identical elements.

FIG. 1 is a perspective view of a first exemplary embodiment of anexpandable spinal fixation system;

FIG. 2 is a front elevational view of an expandable barrel assembly ofthe system shown in FIG. 1, in a pre-expanded condition;

FIG. 3 is a front elevational view of the expandable barrel assemblyshown in FIG. 2, in an expanded condition;

FIG. 3A is a rear elevational view of the expandable barrel assemblyshown in FIG. 2, in an expanded condition;

FIG. 4 is a side elevational view of the expandable barrel assemblyshown in FIG. 2, being inserted between two adjacent spinal processes;

FIG. 5 is a side elevational view of the spinal fixation system shown inFIG. 1, having been inserted between the two adjacent spinal processes;

FIG. 6 is an enlarged side elevational view of an adjustable lockingmechanism of the expandable barrel assembly shown in FIG. 3;

FIG. 7 is a rear elevational view of an alternative embodiment of afixed barrel assembly for use with the spinal fixation system shown inFIG. 1;

FIG. 8 is a side elevational view of the fixed barrel assembly shown inFIG. 7;

FIG. 9 is a side elevational view showing the expansion of theexpandable barrel assembly shown in FIG. 2 by a distractor;

FIG. 10 is a side elevational view showing the insertion of the fixedbarrel assembly shown in FIG. 1 being inserted between the expandablebarrel assembly shown in FIG. 1;

FIG. 11 is a side elevational view showing the spinal fixation systemshown FIG. 1 having been inserted between adjacent spinal processes;

FIG. 12 is a lower perspective view of a second exemplary embodiment ofexpandable fixation system, in a vertically expanded condition;

FIG. 13 is an upper perspective view of the expandable fixation systemshown in FIG. 12, in a vertically contracted condition;

FIG. 14 is a sectional view of the expandable fixation system takenalong lines 14-14 of FIG. 13;

FIG. 15 is a perspective view of an exemplary embodiment of a distractorfor use with the expandable fixation system shown in FIG. 12;

FIG. 16 is a rear perspective view of the distractor shown in FIG. 15,engaged with the expandable fixation system shown in FIG. 12;

FIG. 16A is an enlarged sectional view of the securing member of theexpandable fixation system shown in FIG. 14 in an unsecured condition;

FIG. 16B is an enlarged sectional view of the securing member of theexpandable fixation system shown in FIG. 14 in a lightly securedcondition;

FIG. 16C is a perspective view of the expandable fixation system shownin FIG. 12, in a vertically expanded condition;

FIG. 16D is an enlarged sectional view of the securing member of theexpandable fixation system shown in FIG. 14 in a tightly securedcondition;

FIG. 17 is a front perspective view of the expandable fixation systemshown in FIG. 12 in a separated condition;

FIG. 18 is a front perspective view of another alternative embodiment ofthe fixation system shown in FIG. 12;

FIG. 19 is a front perspective view of an alternative embodiment of anexpandable fixation system;

FIG. 20 is a rear perspective view of an expandable barrel assembly ofthe fixation system shown in FIG. 19;

FIG. 21 is a lateral side elevational view of the expandable barrelassembly shown in FIG. 20, with the expandable barrel assembly in acompressed condition;

FIG. 22 is a lateral side elevational view of the expandable barrelassembly shown in FIG. 20, with the expandable barrel assembly in anexpanded condition;

FIG. 23 is a front perspective view of the expandable fixation systemshown in FIG. 19, with the expandable barrel assembly separated from thefixed barrel assembly;

FIG. 24 is a perspective view of a distractor tool used to insert theexpandable barrel assembly of the system shown in FIG. 19;

FIG. 25 is a perspective view of the distractor tool shown in FIG. 24attached to the expandable barrel assembly of the expandable fixationsystem shown in FIG. 19;

FIG. 26 is a perspective view of the distractor tool shown in FIG. 25,with the fixed barrel assembly inserted into the expandable barrelassembly;

FIG. 27 is a perspective view of an alternative embodiment of anexpandable assembly with an insert for an expandable fixation system inan assembled condition;

FIG. 28 is a perspective view of the expandable fixation system in adisassembled condition;

FIG. 29 is a side elevational view of the expandable assembly shown inFIG. 27, in an engaged condition;

FIG. 30 is a side elevational view of the expandable assembly shown inFIG. 27, in a separated condition;

FIG. 31 is a perspective view of the insert shown in FIG. 27;

FIG. 32 is a perspective view of the expandable fixation system shown inFIG. 27, in an assembled condition, with upper and lower fixation platesin an open position;

FIG. 33 is a perspective view of the expandable fixation system shown inFIG. 32, with the upper fixation plate in a compressed condition;

FIG. 34 is a perspective view of the expandable fixation system shown inFIG. 32, with both the upper fixation plate and the lower fixationplates in a compressed condition;

FIG. 35 is an enlarged perspective view of the upper fixation plate ofthe expandable fixation system shown in FIG. 27;

FIG. 36 is a perspective view of the expandable assembly shown in FIG.27, a separated condition;

FIG. 37 is a sectional view of the expandable fixation system shown inFIG. 32; and

FIG. 38 is a sectional view of a spinous process engagement end of theexpandable fixation system shown in FIG. 32.

DETAILED DESCRIPTION

In the drawings, like numerals indicate like elements throughout.Certain terminology is used herein for convenience only and is not to betaken as a limitation. The terminology includes the words specificallymentioned, derivatives thereof and words of similar import. Theembodiments illustrated below are not intended to be exhaustive or tolimit the invention to the precise form disclosed. These embodiments arechosen and described to best explain the principle of the invention andits application and practical use and to enable others skilled in theart to best utilize the invention.

Reference herein to “one embodiment” or “an embodiment” means that aparticular feature, structure, or characteristic described in connectionwith the embodiment can be included in at least one embodiment. Theappearances of the phrase “in one embodiment” in various places in thespecification are not necessarily all referring to the same embodiment,nor are separate or alternative embodiments necessarily mutuallyexclusive of other embodiments.

As used in this application, the word “exemplary” is used herein to meanserving as an example, instance, or illustration. Any aspect or designdescribed herein as “exemplary” is not necessarily to be construed aspreferred or advantageous over other aspects or designs. Rather, use ofthe word exemplary is intended to present concepts in a concretefashion.

Additionally, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or”. That is, unless specified otherwise, or clearfrom context, “X employs A or B” is intended to mean any of the naturalinclusive permutations. That is, if X employs A; X employs B; or Xemploys both A and B, then “X employs A or B” is satisfied under any ofthe foregoing instances. In addition, the articles “a” and “an” as usedin this application and the appended claims should generally beconstrued to mean “one or more” unless specified otherwise or clear fromcontext to be directed to a singular form.

Unless explicitly stated otherwise, each numerical value and rangeshould be interpreted as being approximate as if the word “about” or“approximately” preceded the value of the value or range.

The use of figure numbers and/or figure reference labels in the claimsis intended to identify one or more possible embodiments of the claimedsubject matter in order to facilitate the interpretation of the claims.Such use is not to be construed as necessarily limiting the scope ofthose claims to the embodiments shown in the corresponding figures.

It should be understood that the steps of the exemplary methods setforth herein are not necessarily required to be performed in the orderdescribed, and the order of the steps of such methods should beunderstood to be merely exemplary. Likewise, additional steps may beincluded in such methods, and certain steps may be omitted or combined,in methods consistent with various embodiments.

Although the elements in the following method claims, if any, arerecited in a particular sequence with corresponding labeling, unless theclaim recitations otherwise imply a particular sequence for implementingsome or all of those elements, those elements are not necessarilyintended to be limited to being implemented in that particular sequence.

The devices and methods described herein are generally directed tomedical devices that can be used to support, stabilize and/or replaceanatomical structures within a body of a patient. In someimplementations, the devices and methods described herein are configuredto provide support to a spine or back of a patient, including providingsupport between two vertebrae in the spine or back of the patient. Inother implementations, other portions of the body of the patient can besupported by the devices described herein. The medical devices describedherein may be implanted within a body of a patient to assist inmaintaining normal physiologic motion in the spine of the patient.

The term patient may be used hereafter for a person who benefits fromthe medical device or the methods disclosed herein. For example, thepatient may be a person whose body receives the medical device disclosedherein in a surgical treatment. For example, in some embodiments, thepatient may be a human female, human male, or any other mammal.

This document describes implementations of an implantable medical devicethat may be used as a posterior, non-pedicle supplemental fixationdevice for use in the non-cervical spine. The medical device may be usedas an interspinous fusion device. The medical device may be implantedwith or without the removal of the supraspinous ligament. In one or moreimplementations, as will be discussed below, the supraspinous ligamentmay be preserved. The medical device may be attached firmly to thespinous processes above and below an interspinous space. The medicaldevice may immobilize a lumbar motion segment posteriorly with no otherdevices implanted. The medical device may withstand compressive,torsional and shear loads seen in the lumbar spine. The medical devicemay be used to achieve supplemental fusion and to treat conditions ofthe spine such as, for example, degenerative disc disease,spondylolisthesis, trauma (i.e., fracture or dislocation), tumors and/orother conditions.

This document describes implementations of an implantable medicaldevice, where the medical device may include a fixed central barrel andan expandable outer barrel with separate upper and lower barrel halves,with each barrel and barrel half having bone contacting endplates. Theplates include projections (e.g., spikes) that bite into the spinousprocess to clamp the device in place. The barrels may angulate relativeto each other to conform to the patient anatomy. The plates may belocked with a set screw and may have a lordotic profile to match thelumbar anatomy. The expandable outer barrel may provide interspinousdistraction, off-loading the spikes on the plate and reducing thechances of breaking the spinous process. The outer barrel may be sizedto fit into the interspinous space without resistance, and thenexpanded. The central barrel may include a graft window anteriorly andposteriorly and may be packed with graft material after expansion usingthe graft window. The endplates may include anatomically-shaped groovesfor optimal bone contact and fit. Optionally, the endplates may beomitted.

In an exemplary embodiment, the device may be constructed from titanium.Optionally, the expandable outer barrel and the fixed central barrel canbe constructed from other material, such as, for example, polyetherether ketone (PEEK) or other suitable biocompatible material.

The present disclosure provides embodiments of expandable spinalfixation assemblies that can be used to achieve supplemental spinalfusion and treating, among others, the following conditions:degenerative disc disease; spondylolisthesis; trauma (i.e., fracture ordislocation); and/or tumor.

Referring to FIGS. 1-11, an expandable spinal fixation system 100(“fixation system 100”) for immobilizing two adjacent spinous processes50, 52, such as, for example, vertebrae in the non-cervical spine,according to a first exemplary embodiment is shown. As used throughoutthis text, spinous process 50 is an upper vertebra and spinous process52 is a lower vertebra, although those skilled in the art will recognizethat spinous processes 50, 52 can be other biological elements instead.

Fixation system 100 includes an expandable barrel assembly 110 having anupper barrel half 112 that is releasably securable to a lower barrelhalf 114 such that upper barrel half 112 and lower barrel half 114 canvertically translate with respect to each other, as shown in FIGS. 2 and3.

Expandable barrel assembly 110 is adapted to be inserted between twoadjacent spinal processes 50, 52, as shown in FIG. 4. Fixation system100 also includes a fixed barrel assembly 160 such that fixed barrelassembly 160 is adapted to be inserted between upper barrel half 112 andlower barrel half 114.

Referring back to FIG. 1, as well as to FIG. 5, barrel half 112 extendsalong an upper longitudinal axis L1 and has an upper barrel distal end116 and an upper barrel proximal end 118, distal from distal end 116.Upper barrel half 112 includes a generally concave inner surface 120extending between the upper barrel distal end 116 and the upper barrelproximal end 118. A slot 122 is formed along the longitudinal length ofconcave inner surface 120.

Upper barrel proximal end 118 comprises an upper plate 124 extending ina first direction generally orthogonally from upper barrel half 112.Upper plate 124 is used to secure spinous process 50 to fixation system100. Upper plate 124 may include multiple projections 126 (e.g.,spikes). While the term spikes may be used for projections 126, othertypes of projections may be used that may have a more tapered point orrounded point or other type of ending to each projection 126.Projections 126 may be integrally formed with upper plate 124 orprojections 126 may be separate components that are secured to upperplate 124. Projections 126 may be pyramid shaped with a base portionsecured or integrally formed on upper plate 124. The sides ofprojections 126 may extend from the base to form a point in the shape ofa pyramid. In other example implementations, projections 126 may beformed into other shapes that raise to a point to enable each projection126 to engage spinous process 50. As discussed above, the end of theeach projection 126 may include tips other than a point such as, forexample, rounded tip, a square tip or other-shaped tip.

While projections 126 are shown in FIG. 1 as being fixed, those skilledin the art will recognize that projections 126 may also be articulatingprojections that provide various degrees of angular articulation as maybe required by the particular anatomy of the patient into which fixationsystem 100 is being inserted.

In an exemplary embodiment, upper plate 124 and projections 126 may bemade of titanium. In other implementations, upper plate 124 andprojections 126 may be made of other biocompatible materials. Upperplate 124 includes a recess 127 formed therein, which sized to accept adistractor insert, as will be discussed later herein.

Referring to FIG. 6, a vertical slot 128 is formed upper barrel proximalend 118, and extends upwardly into plate 124. A threaded hole 130 isformed upper plate 124 and provides communication with vertical slot128.

Referring back to FIGS. 1 and 5, lower barrel half 114 extends along alower longitudinal axis L2 generally parallel to upper longitudinal axisL1, wherein lower longitudinal axis L2 is movable relative to upperlongitudinal axis L1. Lower barrel half 114 also includes a lower barreldistal end 132 and a lower barrel proximal end 134, distal from lowerbarrel distal end 132. Lower barrel half 114 includes a generallyconcave inner surface 136 extending between lower barrel distal end 132and lower barrel proximal end 134.

Lower barrel proximal end 134 includes a tab 140 sized to be slidablyinserted into slot 128 such that lower barrel half 114 is slidinglycoupled to upper barrel half 112 such that lower barrel half 114 isslidable toward upper barrel half 112 to secure fixed barrel assembly160 between upper barrel half 112 and lower barrel half 114. Tab 140includes a plurality of laterally extending recesses 141 extending alonga proximal side thereof.

Lower barrel proximal end 134 also includes a lower plate 142 extendingin a second direction, opposite the first direction of the extension ofupper plate 124, generally orthogonally from lower barrel half 114.Similar to projections 126 extending distally outwardly from upper plate124, lower plate 142 includes a plurality of projections 144 extendingdistally outwardly therefrom. Lower plate 142 also includes a recess 145formed therein, which is sized to accept a distractor insert, as will bediscussed later herein.

While expandable barrel assembly 110 includes upper plate 124 and lowerplate 142, those skilled in the art will recognize that upper plate 124and lower plate 142 can be omitted, allowing the natural compressionbetween spinous processes 50, 52, as well as fixed barrel 160, to retainexpandable barrel assembly 110 in place after its insertion.

Referring now to FIG. 6, barrel assembly 110 further includes a securingassembly 150 having a plate 152 that is adapted to releasably bias tab140 against upper barrel proximal end 118 to secure upper barrel half112 to lower barrel half 114 and to assist in securing spinous processes50, 52 to fixation system 100. Plate 152 includes a laterally extendingrib 154 that is sized to fit into one of recesses 141.

A securing member 156 is adapted to releasably bias plate 152 againsttab 140. Securing member 156 can be a screw that is threadably insertedthrough a threaded hole 130 to allow for releasable biasing of plate 152against tab 140. When securing member 156 biases plate 152 against tab140, lower barrel half 114 is fixed relative to upper barrel half 112.

Referring now to FIGS. 1, 5, 7, and 8, fixed barrel assembly 160 isadapted to be inserted between upper barrel half 112 and lower barrelhalf 114. Fixed barrel assembly 160 has a generally tubular body 162sized to fit between convex inner surface 120 of upper barrel half 112and concave inner surface 136 of the lower barrel half 114. Body 162extends along a longitudinal axis L3.

Fixation system 100 can include a plurality of fixed barrel assemblies160 having bodies 162 of different external diameters to accommodatedifferent amounts of distraction required between adjacent spinalprocesses 50, 52.

Body 162 comprises a distal end 164 having a first tang 166 extendingoutwardly laterally therefrom and a second tang 168 extending outwardlylaterally therefrom, diametrically opposed from first tang 166. Tangs166, 168 act as spacers between upper barrel half 112 and lower barrelhalf 114 and as a fulcrum, as will be described in more detail laterherein.

Body 162 also includes a key 170 extending longitudinally along at leasta portion thereof. Referring to FIG. 3A, slot 122 in concave innersurface 120 of upper barrel half 112 is adapted to receive key 170 whenfixed barrel assembly 160 is inserted into expandable barrel assembly110.

Body 162 further includes a proximal end 172 having a first securingplate 174 extending away from body 162, generally orthogonal tolongitudinal axis L3, and a second securing plate 176 extending awayfrom body 162, generally co-planar with first securing plate 174. Eachof first and second securing plates 174, 176 includes a locking recess178, 180, respectively extending therethrough, such that each lockingrecess 178, 180 is sized to allow for insertion upper barrel distal end116 and lower barrel distal end 132, respectively. Similar toprojections 126 and 144 discussed above, each of the first and secondsecuring plates 174, 176 also includes articulating spikes orprojections 182 extending outwardly distally therefrom. Projections 182are used to engage fixed barrel assembly 160, with spinous processes 50,52.

Instead of fixed projections 182, in an alternative embodiment,articulating spikes 282 may be used, as shown in FIGS. 6 and 7. As shownin FIG. 8, articulating spikes 282 can pivot about longitudinal axes L4,L5 to accommodate a firm connection to spinal processes 50, 52,respectively.

Proximal end 172 also includes a first proximal wing 184 and a secondproximal wing 186 extending outwardly therefrom, such that each of firstproximal wing 184 and second proximal wing 186 has a recess 188, 190,respectively formed therein. Recesses 188, 190 are adapted to receive aninsertion tool, as will be discussed later herein.

Body 162 includes a plurality of radially extending windows 192extending between distal end 164 and proximal end 172. The interior ofbody 162 and windows 192 may be used as graft windows for the packing ofbone graft material prior to or subsequent to the insertion andplacement of fixation system 100 in the patient.

According to one embodiment, a method of installing fixation system 100,for example, at the site of two adjacent spinous processes 50, 52 of thenon-cervical spine, is provided. While those skilled in the art willrecognize that the components of fixation system, i.e. expandable barrelassembly 110 and fixed barrel assembly 160, can be inserted in any orderbased on surgical approach, an exemplary installation process will bedescribed below as inserting expandable barrel assembly 110 first andthen inserting fixed barrel assembly 160 afterward. In principle,fixation system 100 is expandable in-situ, and can be locked in positionbetween spinous processes 50, 52 by a combination of projections/spikes126, 144, 182, 282.

As shown in FIGS. 4, 9, and 10, a distractor 200 is releasablyconnectable to expandable barrel assembly 110 for insertion ofexpandable barrel assembly 110 between adjacent spinal processes 50, 52.Distractor 200 includes a first leg 210 having a distal end 212 that isinsertable into recess 127 in upper plate 124. First leg 210 alsoincludes a proximal end 214, shown in FIG. 9. Distractor 200 furtherincludes a second leg 220 having a distal end 222 that is insertableinto recess 145 in lower plate 142. Second leg 220 also includes aproximal end 224, shown in FIG. 9.

First leg 210 is pivotally connected to second leg 220 at a pivot pin230, such the action of moving proximal end 224 of second leg 220 towardproximal end 214 of first leg 210 spaces distal end 212 of first leg 210away from distal end 222 of second leg 220. A barrel size gauge 232 isconnected to proximal end 214, and includes indicia, such as sizemarkings 234, that, when intersected by proximal end 224 of second leg220, provide an indication of the distraction distance between movementof distal end 212 of first length 210 away from distal end 222 of secondleg 220, and, correspondingly, a distance between spinous processes 50,52. In an exemplary embodiment, an expansion range of greater than about6 mm can be achieved, although those skilled in the art will recognizethat other ranges can be achieved as well.

At this time, expandable barrel assembly 110 is laterally insertedbetween spinal processes 50, 52 in a collapsed configuration, as shownin FIG. 4, and can be pressed against spinous processes 50, 52 such thatprojections 126 embed into spinous process 50 and secure upper plate 124to spinous process 50 and such that projections 144 embed into spinousprocess 52 and secure lower plate 142 to spinous process 52.

Additionally, securing assembly 150 can optionally be operated byscrewing securing member 156 against plate 152 such that rib 154 isforced into a recess 141, thereby stabilizing expandable barrel assembly110, and, consequently, spinous processes 50, 52 in a distracted state,enabling distractor 200 to be removed from expandable barrel assembly110. Alternatively, securing assembly 150 does not necessarily need tobe operated, and distractor 200 can remain temporarily connected toexpandable barrel assembly 110, keeping upper barrel half 112 and lowerbarrel half 114 open in the distracted/expanded state.

While spinous processes 50, 52 are distracted away from each other,fixed barrel assembly 160 can be laterally inserted from an opposingside relative to the insertion of expandable barrel assembly 110. Thesize of fixed barrel assembly 160 to be used can be determined by theamount of distraction, as measured by the barrel size gauge 232 ondistractor 200.

Optionally, prior to insertion of fixed barrel assembly 160, body 162can be packed with graft material. An insertion tool (not shown) isinserted into recesses 188, 190 in their respective wings 184, 186, and,as shown in FIG. 10, fixed barrel assembly 160 is inserted between upperbarrel half 112 and lower barrel half 114. Fixed barrel assembly 160 canbe pivoted about key 170 and/or tangs 166, 168 during insertion tobetter accommodate geometry of spinous processes 50, 52 in order toattain secure placement of fixed barrel assembly 160.

Once fixed barrel assembly 160 is located between upper barrel half 112and lower barrel half 114, securing member 156 can be released, allowingnatural compression of spinous processes 50, 52 to clamp down onexpandable barrel assembly 110 and fixed barrel assembly 160. Fixedbarrel assembly 160 can be further inserted such that distal ends 116,132 of upper barrel half 112 and lower barrel half 114, respectively,engage recesses 178, 180, respectively in fixed barrel assembly 160 andsuch that projections 182 of fixed barrel assembly 160, engage spinousprocesses 50, 52, securing fixed barrel assembly 160 to spinousprocesses 50, 52, as shown in FIG. 11.

The insertion tool can then be removed from fixed barrel assembly 160and, if distractor 200 has not yet been removed from expandable barrelassembly 110, distractor 200 can be removed at this time. If body 162 offixed barrel assembly 160 has not yet been filled with graft material,the graft material can be inserted into body 162 at this time.

An alternative embodiment of an expandable spinal fixation system 300(“fixation system 300”) is shown in FIGS. 12-19. Fixation system 300includes an expandable frame that is expandable in bothcranial-to-caudal and left-to-right directions, with built-in spikeplates to grip adjacent spinal processes. Fixation system 300 can beconstructed from titanium or other biocompatible materials.

Referring specifically to FIGS. 12-15, fixation system 300 includes afirst longitudinal member 310 and a second longitudinal member 330extending generally parallel to first longitudinal member 310. Secondlongitudinal member 330 is adjustable relative to first longitudinalmember 310 such that a spacing between first longitudinal member 310 andsecond longitudinal member 330 can be adjusted based on the width ofspinous processes 50, 52.

A first lateral member 350 has a first collar 352 slidingly disposedalong first longitudinal member 310 and a second collar 354 fixedlydisposed along second longitudinal member 330. A laterally extending rod355 is fixedly connected to second collar 354 and slidingly coupled tofirst collar 352 such that the distance between first longitudinalmember 310 and second longitudinal member 330 can be adjusted to fitparticular spinous processes 50, 52.

Similarly, a second lateral member 370 has a first collar 372 slidinglydisposed along first longitudinal member 310 and a second collar 374fixedly disposed on second longitudinal member 330. A laterallyextending rod 375 is fixedly connected to second collar 374 andslidingly coupled to first collar 372 such that the distance betweenfirst longitudinal member 310 and second longitudinal member 330 can beadjusted to fit particular spinous processes 50, 52.

Second lateral member 370 extends generally parallel to first lateralmember 350, such that members 310, 330, 350, 370 form an expandable andcontractible rectangle, depending on the geometry of spinous processes50, 52. Optionally, a graft window formed by the interior of therectangle can be packed following insertion of fixation system 300 in apatient.

In different exemplary embodiments, fixation system 300 is expandableacross different height ranges. By way of example, a first height rangecan be between about 6 millimeters (“mm”) and about 12 mm; a secondheight range can be between about 8 mm and about 16 mm; and a thirdheight range can be between about 10 mm and about 20 mm. Additionally,in different exemplary embodiments, fixation system 300 is expandableacross different width ranges. By way of example, a first width rangecan be between about 6 mm and about 12 mm; and a second width range canbe between about 8 mm and about 16 mm.

In order to achieve expandability between first lateral member 350 andsecond lateral member 370, longitudinal members 310, 330 are expandablebetween an expanded condition, as shown in FIG. 12, and a contractedcondition, as shown in FIG. 13. As shown in FIG. 14, second longitudinalmember 330 comprises a lower portion 332 and an upper portion 334telescopically connected to lower portion 332. Similarly, firstlongitudinal member 310 comprises a lower portion 312, and an upperportion 314 telescopically connected to lower portion 312.

Lower portion 312, 332, of each longitudinal member 310, 330 isreleasably securable to first lateral member 350, and upper portion 314,334 of each longitudinal member 310, 330 is releasably securable tosecond lateral member 370. Each of lower portion 312, 332 of firstlongitudinal member 310, 330 comprises a ribbed exterior (only ribbedexterior 335 in second longitudinal member 330 is shown).

Referring back to FIGS. 12 and 13, as well as FIG. 14, lower portion 312includes a first spiked member 316 extending medially therefrom. Upperportion 314 includes a second spiked member 318 extending mediallytherefrom. First spiked member 316 comprises a posterior connected end320 that is connected to lower portion 312 and an anterior free end 322.Second spiked member 318 comprises a posterior connected end 328 that isconnected to upper portion 314 and an anterior free end 329. Each offirst spiked member 316 and second spiked member 318 comprises a lateralcavity 325, 326, respectively, disposed between posterior connected end320 and anterior free end 322 of first spiked member 316 and betweenposterior connected end 328 and anterior free end 329 of second spikedmember 318.

While FIG. 13 shows three spikes on each of spiked members 316, 318,those skilled in the art will recognize that spiked members 316, 318,can have more or less than three spikes each. Similarly to first spikedmember 316, second spiked member 318 also comprises a posterior fixedend 324 and an anterior free end 327. The spikes on spiked members 316,318 are used to fixedly secure first longitudinal member 310 to spinousprocesses 50, 52. As fixation device 300 is being located on thepatient's spine, spiked members 316, 318 are driven into spinousprocesses 52, 50, respectively, to secure fixation device 300 to thespine.

Similar to first longitudinal member 310, second longitudinal member 330includes a first spiked member 336 extending medially therefrom. Upperportion 334 includes a second spiked member 338 extending mediallytherefrom. First spiked member 336 comprises a posterior connected end340 that is connected to lower portion 322 and an anterior free end 342.Second spiked member 338 comprises a posterior connected end 348 that isconnected to upper portion 334 and an anterior free end 349. Each offirst spiked member 336 and second spiked member 338 comprises a lateralcavity 345, 346, respectively, disposed between posterior connected end340 and anterior free end 342 of first spiked member 336 and betweenposterior connected end 348 and anterior free end 349 of second spikedmember 338.

In an exemplary embodiment, a first configuration of a securing member353 is adapted to releasably secure first lateral member 350 to lowerportion 312 of first longitudinal member 310 and to lower portion 332 ofsecond longitudinal member 330. As shown in FIG. 12, securing member 353can be a screw that requires a spanner wrench (not shown) to rotate.Further, a second configuration of a securing member 373 can be adaptedto releasably secure second lateral member 370 to upper portion 314 offirst longitudinal member 310 and to upper portion 334 of secondlongitudinal member 330. As shown in FIG. 12, securing member 373 can bea screw that requires a TORX® wrench (not shown) to rotate.Alternatively, as shown in FIGS. 16A-16D, securing member 373 can be anAllen head screw. Additionally, as shown in FIG. 14, second lateralmember 370 securing member 373 includes an insert 371 that has a ribbedengagement surface 376 adapted to releasably engage ribbed exterior 335of lower portion 332 in order to releasably secure upper portion 334 tolower portion 332. Although not shown, a similar configuration isprovided with respect to first longitudinal member 310 in order toreleasably secure upper portion 314 to lower portion 312.

Second lateral member 370 also includes an engagement eye 377 extendinglaterally from first longitudinal member 310 and an engagement eye 378extending laterally from second longitudinal member 330.

An exemplary distractor 400 that can be used to implant fixation device300 into a patient (not shown) is shown in FIG. 15 and the connection ofdistractor 400 with fixation device 300 is shown in FIG. 16.

Distractor 400 includes a distal end 410 that is releasably connectableto fixation device 300, and a proximal end 440 that is gripped andcompressed by a user to open distal end 410. Distractor 400 includes atop leg 420 that is pivotally connected to a second leg 430 at a pivot432 such that, when proximal end 440 is compressed, distal end 410expands so that top leg 420 and bottom leg 430 separate from each other.

Proximal end 440 includes a biasing member 442 that is disposed betweentop leg 420 and bottom leg 430 such that from a compressed state asdescribed immediately above, when compression force is released, biasingmember 442 biases top leg 420 and bottom leg 430 away from each otheralong distal end 440. In an exemplary embodiment, biasing member 442 canbe a leaf spring, although those skilled in the art will recognize thatbiasing member 442 can be helical springs or other suitable biasingmembers.

Proximal end 440 also includes a scale 444 that is calibrated todetermine the amount of separation between first lateral member 350 andsecond lateral member 370. When fixation device 300 is being inserted,the inserting surgeon can read scale 444 to determine how far spinousprocess 50 is being separated form spinous process 52.

Distal end 410 includes two pair of articulating insertion arms thatreleasably engage with fixation device 300 to attached fixation device300 to spinous processes 50, 52. Top leg 420 includes an upper arm 421that is pivotally connected to top leg 420 at a pivot 412. Upper arm 421also includes a pin 423 that is sized to fit into engagement eye 377 onsecond lateral member 370. Top leg 420 also includes a lower arm 426that is pivotally connected to top leg 420 along the axis of pivot 422.Lower arm 426 also includes a pin 427 that is sized to fit intoengagement eye 378 on second lateral member 370.

Bottom leg 430 includes an upper arm 431 that is pivotally connected tobottom leg 430 at a pivot 432. Upper arm 431 also includes a pin 433that is sized to fit into securing member 353 on first lateral member350 at first longitudinal member 310. Bottom leg 430 also includes alower arm 436 that is pivotally connected to bottom leg 430 along theaxis of pivot 432. Lower arm 436 also includes a pin 437 that is sizedto fit into securing member 353 on first lateral member 350 at secondlongitudinal member 330.

With the distance between first longitudinal member 310 and secondlongitudinal member 330 of fixation device 300 adjusted to accommodatethe width of the specific spinal processes 50, 52 at issue, distractor400 is attached to fixation device 300 as shown in FIG. 16. Spikedmembers 318, 338 are forced into spinous process 50 and spiked members316, 336 are forced into spinous process 52. At this time, ribbedengagement surface 376 is disengaged from ribbed exterior 335, as shownin FIG. 16A. Distractor 400 is then used to separate first lateralmember 350 from second lateral member 370, thus opening the distancebetween spinous process 50 and spinous process 52, to a position asshown in FIG. 12. With spinous process 50, 52 separated, securingmembers 373 on first collar 372 and second collar 374 are slightlytightened for a light interference engagement, as shown in FIG. 16B,which locks the vertical distance between first lateral member 350 andsecond lateral member 370, but still allows for compression of firstlongitudinal member 310 and second longitudinal member 330 toward eachother.

Then, referring to FIG. 16C, first longitudinal member 310 is compressedin the direction of arrow “A” and second longitudinal member 330 iscompressed in the direction of arrow “B” to set the lateral spacingbetween first longitudinal member 310 and second longitudinal member330. Securing members 373 on first collar 372 and second collar 374 arecompletely tightened for a tight interference engagement, as shown inFIG. 16D, locking members 310, 330, 350, 370 in place relative to eachother. Optionally, graft material (not shown) can be packed in thewindow defined by first longitudinal member 310, second longitudinalmember 330, first lateral member 350, and second lateral member 370.

Fixation device 300 with distractor 400 is designed to be implantedusing a posterior insertion method. If, however, in order to spare theligaments, a lateral insertion is desired, fixation device 300 can bedisassembled, as shown in FIG. 17, such that rails 355, 375 areseparated from their respective first collars 352, 372.

First longitudinal member 310 can be inserted laterally from one side ofspinous processes 50, 52, and second longitudinal member 330, with firstand second lateral members 350, 370, can be inserted laterally from anopposing side of spinous processes 50, 52 such that rails 355, 375 canbe inserted into their respective first collars 352, 372.

In an alternative embodiment of a fixation device 500, shown in FIG. 18,instead of connecting distractor 400 to engagement eyes 377, 378 andsecuring members 353, rails 555, 575 each have a pair of inwardly facingslots 556, 558, and 576, 578, respectively, into which legs of adistractor (not shown) can be inserted to separate rails 55, 575 fromeach other.

Referring to FIGS. 19-26, a spinous process fixation assembly 600(“fixation assembly 600”) according to a first exemplary embodiment isshown. Fixation assembly 600 is a posterior, non-pedicle supplementalfixation device, intended for use in the non-cervical spine, whichallows for the alternative selection of insertion of a fixed portionfrom a lateral direction or from a posterior-to anterior direction. Withthe option to preserve the supraspinous ligament, fixation assembly 600is intended to attach firmly to adjacent spinous processes 50, 52 andimmobilize a lumbar motion segment posteriorly. Fixation assembly 600 isexpected to withstand compressive, torsional, and shear loads seen inthe lumbar spine.

Fixation assembly 600 includes an expandable barrel assembly 610 and afixed barrel assembly 670 that is insertable into expandable barrelassembly 610 such that expandable barrel assembly 610 can be compressedto engage and retain fixed barrel assembly 670 therein. An insertiontool, such as a distractor 700 (shown in FIGS. 24-26) is part offixation assembly 600 and is used to insert and to vertically adjustexpandable barrel assembly 610 in situ.

Expandable barrel assembly 610 includes an upper barrel half 612 and alower barrel half 642 such that lower barrel half 642 is verticallyadjustably connected to upper barrel half 612. Upper barrel half 612includes an upper barrel proximal end 614 and an upper barrel distal end616, distal from proximal end 614.

Upper barrel half 612 includes a vertical plate 620 that is used toengage an upper spinous process 50 (shown in FIG. 4). Plate 620 includesa plurality of medially extending spikes (not shown for clarity) thatengage spinous process 50 and secure upper barrel half 612 to spinousprocess 50. Plate 620 includes a posterior notch 622 for engagement withdistractor 700, as will be discussed later herein.

A first generally planar arm 624 extends between the upper barrelproximal end 614 and upper barrel distal end 616. A gusset 625 extendsupwardly from arm 624 and connects to plate 620, providing structuralstability between arm 624 and plate 620. A first arcuate portion 628 ofarm 624 extends anteriorly downwardly from arm 624.

Arm 624 at a distal end 616 of upper barrel half 612 includes a firstgenerally U-shaped opening 626. Opening 626 is sized to allow forengagement with an upper portion of fixed barrel assembly 670.

A post 630 extends downwardly from plate 620. Post 630 includes aplurality of posteriorly facing ratchet teeth 632 and correspondinganteriorly facing ratchet teeth 634 that are used to adjust the heightof upper barrel half 612 with respect to lower barrel half 642.

Lower barrel half 642 has a lower barrel proximal end 644 and a lowerbarrel distal end 646, distal from lower barrel proximal end 644. Lowerbarrel half 642 includes a vertical plate 650 that is used to engage alower spinous process 52 (shown in FIG. 4). Plate 650 includes aplurality of medially extending spikes (not shown for clarity) thatengage spinous process 52 and secure lower barrel half 642 to spinousprocess 52. Plate 650 includes a posterior notch 652 for engagement withdistractor 700, as will be discussed later herein.

A second generally planar arm 654 extends between lower barrel proximalend 644 and lower barrel distal end 646. A gusset 655 extends downwardlyfrom arm 654 and connects to plate 650, providing structural stabilitybetween arm 654 and plate 650. A second arcuate portion 658 of arm 654extends anteriorly upwardly from arm 654 such that, when lower barrelhalf 642 and upper barrel half 612 are translated vertically toward eachother, arcuate portion 658 and arcuate portion 628 form an anteriorobstruction that precludes the advancement of fixed barrel assembly 670anteriorly.

Arm 654 at distal end 646 of lower barrel half 642 includes a secondgenerally U-shaped opening 656. Opening 656 is sized to allow forengagement with a lower portion of fixed barrel assembly 660.

A receiver 660 extends laterally from proximal end 644 of lower barrelhalf 642. Receiver 660 is sized and adapted to receive post 630, suchthat post 630 is movable within receiver 660. Referring to FIG. 22,receiver 660 includes an internal tooth 662 that extends anteriorly intoreceiver 660 to engage ratchet teeth 632 on post 630. Similarly,receiver 660 includes an internal tooth 664 that extends posteriorlyinto receiver 660 to engage ratchet teeth 634 on post 630. Receiverteeth 662, 664 and ratchet teeth 632, 634 combine to form a ratchetassembly connecting upper barrel half 612 to lower barrel half 642 suchthat the ratchet assembly provides for relative vertical movement ofupper barrel half 612 with respect to lower barrel half 642, but alsorestricts vertical movement without the use of distractor 700.

Referring to FIGS. 19 and 23, fixed barrel assembly 670 has a body 672that is sized to fit between upper barrel half 612 and lower barrel half642 in one of an anterior-to-posterior direction and a lateraldirection. Body 672 has an arcuate anterior side 674 that is adapted toengage first arcuate portion 628 on upper barrel half 612 and secondarcuate portion 658 on lower barrel half 642. Anterior side 674 includesan anterior projection 676 that fits between first arcuate portion 628and second arcuate portion 658 and acts as a key to guide fixed barrelassembly 670 into position between upper barrel half 612 and lowerbarrel half 642. Body 672 is hollow and includes a proximal opening 673that is sized to allow for the insertion of graft material (not shown)after insertion of fixation assembly 600 into the patient. Body 672 alsohas a notch 675 formed at a distal end thereof. Notch 675 is sized toreceive post 630 and receiver 660 when fixed barrel assembly 670 isinserted into expandable barrel assembly 610 from a lateral direction.

Fixed barrel assembly 670 further includes an upper plate 678 thatextends upwardly from body 672. Upper plate 678 includes a plurality ofmedially extending spikes (not shown for clarity) that engage spinousprocess 50. Upper plate 678 also includes a first notched portion 680that connects upper plate 678 to body 670. Notched portion 680 includesa posterior notch 682 and an anterior notch 684. Notches 682, 684 aresized to accept arm 624 on either side of U-shaped opening 626 such thatnotched portion 680 extends into U-shaped opening 626.

Fixed barrel assembly 670 also includes a lower plate 686 extendingdownwardly therefrom. Lower plate 686 includes a plurality of mediallyextending spikes (not shown for clarity) that engage spinous process 52.Lower plate 686 includes a second notched portion 688 that connectslower plate 686 to body 670. Notched portion 688 includes a posteriornotch 690 and an anterior notch 692. Notches 690, 692 are sized toaccept arm 654 on either side of U-shaped opening 656 such that notchedportion 688 extends into U-shaped opening 656.

While, in an exemplary embodiment, fixation assembly 600 can be madefrom titanium, those skilled in the art will recognize that fixationassembly 600 can be made from other biocompatible materials, such as,for example, PEEK or allograft, with plates 620, 650, 678, 686 beingconstructed from titanium, for example.

An exemplary distractor 700 is shown in FIGS. 24-26 and is used tomanipulate expandable barrel assembly 610. Distractor 700 includes afirst leg 702 and a second leg 704, attached to each other at a centralportion 706 by a pivot pin 708.

First leg 702 includes a distal first finger 710 that is adapted toreleasably engage upper barrel half 612. Second leg 704 includes adistal second finger 720 that is adapted to releasably engage lowerbarrel half 642 such that operation of distractor 700 vertically adjustsupper barrel half 612 with respect to lower barrel half 642 by movingupper barrel half 612 relative to lower barrel half 642 against theratchet assembly. Embodiment, distractor 700 can be pre-packaged alreadyattached to expandable barrel assembly 610.

First leg 702 also includes a first proximal handle end 714 and secondleg 704 includes a second proximal handle end 724 that are gripped by aused. A distance gauge 730 is provided between first proximal handle end714 and second proximal handle end 724 to indicate how far upper barrelhalf 612 is spaced from lower barrel half 642.

According to one embodiment, a method of installing fixation assembly600 600, for example, at the site of spinous processes 50, 52, mayinclude inserting first finger 710 into notch 622 in upper barrelassembly 612 and inserting second finger 720 into notch 652 in lowerbarrel assembly 642. Next, expandable barrel assembly 610 can beexpanded to a desired height, as measured by distance gauge 730 ondistractor 700. This measured value will determine the size of fixedbarrel assembly 670.

Fixed barrel assembly 670 can be inserted into expandable barrelassembly 610 in one of two ways. For a lateral approach, fixed barrelassembly 670 can be inserted laterally from the distal end of expandablebarrel assembly 610 and fit between upper barrel half 612 and lowerbarrel half 642.

For an alternative posterior-to-anterior surgical approach, fixed barrelassembly 670 can be inserted from the posterior side, such that anteriorprojection 676 is located between arcuate portion 628 of arm 624 onupper barrel half 612 and arcuate portion 658 of arm 654 on lower barrelhalf 642, which both act as a positive stop to prevent barrel 672 frombeing advanced too far anteriorly. Once located, the upper barrel half612, lower barrel half 642, and fixed barrel half 670 can be compressedtogether against the spinous processes 50, 52. Fixed barrel half 670 canthen be optionally back-filled with bone graft material.

The expansion of upper barrel half 612 and lower barrel half 642 isachieved using distractor 700. With the exemplary ratchet assembly, itis only possible to open upper barrel half 612 and lower barrel half 642when distractor 700 is attached to fixation assembly 600. This will alsoprevent an expanded implant from collapsing should distractor 700 beremoved prior to placement of a correctly sized fixed barrel assembly670. Fixation assembly 600 will ratchet together as distractor 600compresses upper barrel half 612 and lower barrel half 642 toward eachother, locking the construct.

The expandable upper barrel half 612 and lower barrel half 642 allowfixation assembly 600 to be inserted at a minimum height and alsoprovide interspinous distraction, off-loading the spikes on theirrespective plates 620, 650, 678, 686 and reducing the chances ofbreaking either spinous process 50, 52. Adjustable barrel assembly 610is inserted at a collapsed height small enough to fit into theinterspinous space between spinous processes 50, 52 without resistance(between about 4 mm and about 6 mm), and expand upper barrel half 612away from lower barrel half 642.

Alternatively, the upper and lower halves 612, 642, respectively, do notneed to be connected or locked in place. In such a design, distractor700 would keep barrel halves 612, 642 open in the distracted/expandedstate until fixed barrel assembly 670 is inserted. When distractor 700is released, barrel halves 612, 642 settle on the barrel 672, whichkeeps the construct in the formerly expanded state. Undersizing ofbarrel 672 will also help prevent over distraction of the interspinousspace, causing kyphosis.

An alternative embodiment of a spinous process fixation assembly 800(“fixation assembly 800”) is shown in FIGS. 27-38. Fixation assembly 800allows for separate adjustment of fixation plates, depending upon theparticular anatomy of spinous processes 50, 52 in a patient.

Fixation assembly 800 includes an upper plate half 810, a lower platehalf 870, and an insert 880 that is inserted in a posterior-to-anteriordirection between upper plate half 810 and lower plate half 870. Upperplate half 810 and lower plate half 870 begin in a low-profile state, asshown in FIG. 29, that allows for insertion with an integratedholder/distractor (not shown) at a height of between about 4 mm andabout 6 mm. Upper plate half 810 and lower plate half 870 can beseparated from each other, as shown in FIG. 30, allowing for theselection of an appropriate sized insert 880 (shown in FIG. 31) to fittherebetween, forming fixation assembly 800, shown in FIG. 32.

As shown in the progression of fixation assembly 800 from FIG. 32-FIG.34, upper plate half 810 and lower plate half 870 can each haveinsertion plates that are spaced apart from each other; only upper platehalf 810 has insertion plates compressed medially toward each other; andboth upper plate half 810 and lower plate half 870 has insertion platescompressed medially toward each other, respectively. The ability toindependently compress upper plate half 810 and lower plate half 870with respect to each other allows for a superior fit for the patient'sanatomy, particularly in cases where the superior spinous process 50 andinferior spinous process 52 are considerably different.

Upper plate half 810 includes a generally planar base 812 having a firstand 814, and a second end 816, distal from first end 814. First end 814includes a fixed plate 818 that extends upwardly therefrom. A pluralityof spikes 820 extending medially inwardly from fixed plate 818. Spikes820 are used to engage spinous process 50 (shown in FIG. 4). A gusset822, located at the medial intersection of first end 814 and fixed plate818, provides structural support for plate 818 relative to base 812.

Second end 816 includes a slidable plate 830 that is mediallytranslatable toward fixed plate 818. Plate 830 is shown in detail inFIG. 38. Plate 830 includes a plurality of spikes 832 extending mediallyinward from slidable plate 830. Spikes 832 are used to engage anopposing side of spinous process 50 from fixed plate 818. Slidable plate830 includes a sliding base 834, with a gusset 833, located at themedial intersection of plate 830 and sliding base 834, providingstructural support for plate 830 relative to sliding base 834.

Base 834 has a generally dovetail or trapezoidally shaped cross-section,with a superior surface 838 at gusset 833 having a smaller length thanan inferior surface 840, so that base 834 can slide a track in upperplate half base 812, as will be discussed herein.

Base 834 also includes a lateral spacer 835. An inferior tab 836cantilevers medially from lateral spacer 835, forming a clevis-shapedopening 839 that allows for the biasing of inferior tab 836 in an upwarddirection as plate 830 is traversed medially. Tab 836 includes a tooth841 extending downwardly therefrom to engage insert 880, allowingslidable plate 832 translate medially, but not laterally.

As shown in FIGS. 28 and 37, base 812 includes a cavity 850, along whichbase 834 slides. Cavity 850 includes sloping anterior and posteriorsides 852, 854, respectively, providing a mating engagement withdovetail or trapezoidally shaped base 834 to prevent base 834 of plate830 from being able to separate superiorly from base 812. While fixationassembly 800 uses a dovetail connection as described above, thoseskilled in the art will recognize that other types of connections, suchas, for example, a T-slot connection, can be used.

Base 812 includes an anterior side portion 856 that extends fartherinferiorly than posterior side portion 858. Insert 880 is inserted froma posterior-to-anterior direction and the longer anterior side portion856 act as a positive stop to prevent insert 880 from falling into thepatient's spinal canal. Additionally, posterior side portion 858 at eachof first end 814 and second end 816 extends farther inferiorly than amedial portion of posterior side portion 858, and also act as a positivestop to prevent insert 880 from traversing laterally with respect toupper plate half 810 and lower plate half 870.

Lower plate 870 is a mirror image of upper plate 810 across plane “P1”that extends orthogonally from the plane of the paper of FIG. 29, so thefeatures of lower plate 870 need not be described in detail.

Referring FIGS. 28, 31, and 38, insert 880 is a generally hollowparallelepiped shaped device having a top surface 882, a posteriorsurface 884, an anterior surface 886, and opposing lateral surfaces 888,890. A bottom surface 892 is a mirror image of top surface 882 aboutplane “P2” extending orthogonally from the plane of the paper of FIG.38, so the features of bottom surface 892 need not be described indetail. Insert 880 can be constructed from PEEK, titanium, allograft orother biocompatible material.

Top surface 882 includes a plurality of spaced openings 894 extendingbetween lateral surfaces 888, 890 that are sized to allow tooth 841 toratchet into as base 830 is traversed medially along cavity 850.

Top surface 882 also includes anterior and posterior rails 896, 898,respectively, that each extends in a medial-to-lateral direction. Rails896, 898 support base 834, allowing tab 836 and tooth 841 to springupward and over top surface 882, between openings 894 when plate 830 iscompressed toward fixed plate 818.

Anterior rail 896 extends only about half the length of insert 880,while posterior rail 989 extends between first end 814 and second end816 of upper plate half 810 such that, when insert 880 is insertedbetween upper plate half 810 and lower plate half 870, no gap is presentbetween upper plate half 810 and insert 880, as well as between lowerplate half 870 and insert 880.

Posterior surface 884 includes an opening 899 formed therein to allowthe insertion of graft material into insert 880, if desired.

In the event that it is desired to remove insert 880 after implantationfor replacement with a different insert having a different height, upperplate half 810 and lower face has 170 can be slightly distracted fromeach other, disengaging tooth 841, from the opening 894 into which ithas been inserted, allowing insert 882 the posteriorly removed fromfixation assembly 800.

Alternatively, although not shown, adjustable plates of fixationassembly 800 can be incorporated into fixation assembly 600 to allow forboth vertical and lateral/medial adjustment of the assembly according tothe particular patient anatomy.

It will be further understood that various changes in the details,materials, and arrangements of the parts which have been described andillustrated in order to explain the nature of this invention may be madeby those skilled in the art without departing from the scope of theinvention as expressed in the following claims.

What is claimed is:
 1. An expandable spinal fixation system comprising:an expandable barrel assembly having: an upper barrel half having: anupper barrel proximal end; and an upper barrel distal end, distal fromthe proximal end; and a lower barrel half having: a lower barrelproximal end; and a lower barrel distal end, distal from the lowerbarrel proximal end; and a fixed barrel assembly having a body sized tofit between the upper barrel half and the lower barrel half in one of aposterior-to-anterior direction and a lateral direction; and theexpandable spinal fixation system, further comprising a ratchet assemblyconnecting the upper barrel half to the lower barrel half such that theratchet assembly provides for relative vertical movement of the upperbarrel half with respect to the lower barrel half; wherein the ratchetassembly comprises a tab extending downwardly from the proximal end ofthe upper barrel half, and wherein the ratchet assembly furthercomprises a receiver extending laterally from the proximal end of thelower barrel half, the receiver adapted to receive the tab, such thatthe tab is movable within the receiver.
 2. The expandable spinalfixation system according to claim 1, wherein the upper barrel halfcomprises a first generally planar arm extending between the upperbarrel proximal end and the upper barrel distal end and a first arcuateportion extending anteriorly downwardly from the first generally planararm.
 3. The expandable spinal fixation system according to claim 2,wherein the upper barrel half distal end has a first generally U-shapedopening in the first planar arm.
 4. The expandable spinal fixationsystem according to claim 2, wherein the lower barrel half comprises asecond generally planar arm extending between the lower barrel proximalend and the lower barrel distal end and a second arcuate portionextending anteriorly upwardly from the second generally planar arm suchthat, when the upper barrel half is vertically moved toward the lowerbarrel half, the first arcuate portion engages the second arcuateportion.
 5. The expandable spinal fixation system according to claim 4,wherein the lower barrel half distal end has a second generally U-shapedopening in the second planar arm.
 6. The expandable spinal fixationsystem according to claim 5, wherein the body of the fixed barrelassembly has an arcuate anterior side adapted to engage the firstarcuate portion and the second arcuate portion.
 7. The expandable spinalfixation system according to claim 6, wherein the fixed barrel assemblyfurther comprises an upper plate extending upwardly therefrom and alower plate extending downwardly therefrom.
 8. The expandable spinalfixation system according to claim 7, wherein the upper plate comprisesa first notched portion connecting the upper plate to the body, andwherein the lower plate comprises a second notched portion connectingthe lower plate to the body.
 9. The expandable spinal fixation systemaccording to claim 8, wherein, when the expandable barrel assembly isadvanced toward the fixed barrel assembly, the first notched portionextends into the first generally U-shaped opening and the second notchedportion extends into the second generally U-shaped opening.
 10. Anexpandable spinal fixation system comprising: an insert comprising: anexpandable barrel assembly having: an upper barrel half having: an upperbarrel proximal end; and an upper barrel distal end, distal from theproximal end; and a lower barrel half adjustably connected to the upperbarrel half, the lower barrel half having: a lower barrel proximal end;and a lower barrel distal end, distal from the lower barrel proximalend; and a fixed barrel assembly having a body sized to fit between theupper barrel half and the lower barrel half in one of ananterior-to-posterior direction and a lateral direction; and aninsertion tool having a first finger adapted to releasably engage theupper barrel half and a second finger adapted to releasably engage thelower barrel half such that operation of the insertion tool verticallyadjusts the upper barrel half with respect to the lower barrel half; andthe expandable spinal fixation system, further comprising a ratchetassembly connecting the upper barrel half to the lower barrel half suchthat the ratchet assembly provides for relative vertical movement of theupper barrel half with respect to the lower barrel half; wherein theratchet assembly comprises a tab extending downwardly from the proximalend of the upper barrel half, and wherein the ratchet assembly furthercomprises a receiver extending laterally from the proximal end of thelower barrel half, the receiver adapted to receive the tab, such thatthe tab is movable within the receiver.
 11. The expandable spinalfixation system according to claim 10, wherein the upper barrel halfcomprises an upper plate extending upwardly therefrom and wherein thelower barrel half comprises a lower plate extending outwardly therefrom.12. The expandable spinal fixation system according to claim 11, whereinthe upper plate comprises a first notched portion connecting the upperplate to the proximal end of the upper barrel half and wherein the lowerplate comprises a second notched portion connecting the lower plate tothe proximal end of the lower barrel half.
 13. The expandable spinalfixation system according to claim 12, wherein the first finger isreleasably insertable into the first notch and wherein the second fingeris releasably insertable into the second notch.
 14. The expandablespinal fixation system according to claim 10, wherein the upper barrelhalf comprises a tab extending toward the lower barrel half, and whereinthe lower barrel half comprises a receiver adapted to receive the tab.15. The expandable spinal fixation system according to claim 14, whereinthe tab and the receiver comprising ratchet assembly.
 16. The expandablespinal fixation system according to claim 15, wherein the insertion toolis configured to move the upper barrel half relative to the lower barrelhalf against the ratchet assembly.